JP4402743B1 - Insulator heater and in-furnace heater using the same - Google Patents

Abstract

An object of the present invention is to satisfactorily prevent a short circuit at a folded tip portion of each double line portion of a heating wire.
An in-furnace heater 1 includes a plurality of heating wires 11 each having a folded tip portion 11a and a double wire portion 11b. An in-furnace heater heater 12 is disposed on the tip side of each heating wire 11. The insulator 12 includes a base plate portion 12a having a plurality of sets S of line insertion holes through which each double line portion 11b passes. The base plate portion 12a protrudes radially around the reference line L, and a first partition wall 12c that partitions the set S of line insertion holes for each set so that adjacent folded tip portions 11a are not short-circuited, and the first partition The protruding end of the wall 12c is connected in a cylindrical shape, and all of the line insertion holes 12a1 and the inner peripheral surface of the protective tube 31 are arranged so that none of the folded tip portions 11a is short-circuited with the inner peripheral surface of the protective tube 31 (protective cover). And a second partition wall 12d for partitioning.
[Selection] Figure 13

Description

  The present invention relates to an insulator for an in-furnace heater and an in-furnace heater using the same, and more particularly to an insulator disposed on the leading end side of a heating wire and an in-furnace heater using the insulator.

  As an insulator for this type of in-furnace heater, usually, a structure in which a plurality of heating wires are inserted into holes of a plurality of stacked insulating support insulators, or a heating wire is used as described in Patent Document 1 below, for example. What is arrange | positioned in the heat generating coil formed by spirally winding is known. In Patent Document 1, a plurality of plate-like first short-circuit prevention bodies are provided at the base of the insulator, and a plate-like second short-circuit prevention body is provided at the tip of each first short-circuit prevention body. And the attachment position and shape of each 1st short circuit prevention body are set so that an insulator can move, rotating between the pitches of a heating coil.

Japanese Patent Laid-Open No. 10-162943

  In addition to the form in which the heating wire is spirally wound as described in Patent Document 1, the heating wire extends from the proximal end toward the distal end, is folded at the distal end side, and returns to the proximal end side again. In some cases, a plurality of sets of double line portions having such a folded shape are provided. Usually, according to the heating wire of the latter form, since the length of the effective heat generating part can be set longer than that of the heating wire of the former form, it is possible to obtain a larger output (heat generation amount). In this case, in the heating wire of the latter form, the insulator extends from the base end to the tip end of the heating wire in order to prevent a short circuit between the double wire portions of each set and between the sets of adjacent double wire portions. In many cases, a plurality of heating wires in the double wire portion are arranged so as to pass through alone.

  However, as shown in FIG. 21, for example, in the latter form in which a plurality of insulators 130 are arranged, the heating wire 110 undergoes linear expansion due to heat generated by energization, and the folded tip portion 110a (loop portion) in each double wire portion 110b. It may be thermally deformed to spread. For this reason, there existed a problem that the heating wire 110 will be short-circuited and disconnected, when adjacent folding front-end | tip parts 110a contact.

  The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to fold back the heating wire in each double wire portion even if the heating wire of the latter form is linearly expanded due to heat generated by energization. An object of the present invention is to provide an in-furnace heater heater that can satisfactorily prevent a short circuit at the tip, and an in-furnace heater using the insulator.

Means for Solving the Problems and Effects of the Invention

  In order to solve the above-described problems, the present invention has a plurality of sets of double line portions each having a heating wire folded back shape that extends from the proximal end toward the distal end, is folded back at the distal end side, and returns to the proximal end side. In order to prevent short-circuiting between the double wire portions of each other and between sets of adjacent double wire portions, a plurality of heating wires of the double wire portions are individually passed from the proximal end to the distal end of the heating wire. Among the plurality of in-furnace heater heaters, the insulator disposed at the tip of the plurality of in-furnace heater heaters has a wire insertion hole through which one double line portion of each set passes. A base plate part having a set around the reference line at a predetermined angular interval is provided, and the base plate part has a radial shape centered on the reference line at the folded tip end side of each double line part of the heating wire. To avoid short circuiting between adjacent folded tips The first partition wall that partitions the set of insertion holes for each set and the projecting ends of the first partition walls are connected in a cylindrical shape, and the folded tip ends are in a direction away from the reference line on the outer periphery of the base plate portion. The second partition wall partitioning so as not to exceed is integrally formed.

  When this insulator for an in-furnace heater is used, an arbitrary set of a plurality of sets of double line portions is located between adjacent ones of the first partition walls and is folded in the vicinity of the first partition walls. It comes to be. In other words, the line portion that protrudes from the line insertion hole in the “going direction” of the base plate portion toward the tip side is folded in the vicinity of the adjacent first partition wall and passes through the line insertion hole in the “return direction” of the base plate portion. And return to the base end. These first partition walls prevent a plurality of sets of double line portions from coming into contact with each other at a portion extending from the line insertion hole of the base plate portion toward the tip side (short circuit). In other words, even if heat is deformed due to heat generated by energization so that the loop at the folded tip end of each double line portion spreads out, there is a first partition wall, so that it approaches that side of the adjacent double line portion. Is prevented and short circuit is prevented.

  Further, in order to solve the above-mentioned problems, the present invention has a plurality of sets of double line portions extending from the proximal end toward the distal end, folded back at the distal end side, and returned to the proximal end side to form the heating wire. In order to prevent a short circuit between the double line parts of each set and between the sets of adjacent double line parts, each heating line of the double line part is allowed to pass independently from the base end to the tip end of the heating line. A plurality of in-furnace heater heater insulators, adjacent ones of the in-furnace heater heaters can be connected to each other, and the plurality of in-furnace heater heaters in a connected state are mounted. A furnace heater in which a cylindrical metal protective cover is attached to the outside of the assembly of the heating wire with the insulator, and is disposed at the tip of the plurality of insulators for the furnace heater. Choshi is the double line part of each set A base plate portion having a set of wire insertion holes that pass through one by one at a predetermined angular interval around the reference line is provided, and the base plate portion of the double-wire portion of the heating wire has a folded tip portion side. The first partition wall that projects radially around the reference line and partitions the set of wire insertion holes for each set so that adjacent folded tip portions do not short-circuit, and the projecting ends of the first partition walls are connected in a cylindrical shape In addition, the second partition wall that partitions all of the line insertion holes and the inner peripheral surface of the protective cover is integrally formed so that none of the folded tip portions are short-circuited with the inner peripheral surface of the protective cover. And

  Further, when the in-furnace heater of the present invention is used, the cylindrical second partition wall even if the folded tip portion of each double line is warped in a direction away from the central reference line due to heat generated by energization. Therefore, the folded tip portion that is thermally deformed so as to warp hits the cylindrical second partition wall, thereby preventing contact (short circuit) with the inner peripheral surface of the protective cover.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows schematically the heating furnace which applied the insulator for furnace heaters which concerns on this invention, and the furnace heater using the same. The perspective view of the assembly of the heater main body (heater with a lever) which comprises the principal part of the in-furnace heater shown in FIG. FIG. 3 is a perspective view of the heating wire shown in FIG. 2. The perspective view of each insulator shown in FIG. The perspective view which shows the connection state of the insulators 12 and 13 shown in FIG. The elements on larger scale of FIG. (A) is a perspective view which shows the connection state of heating wires before connecting the heating wire and heater terminal shown in FIG. (B) is a front view of (a). The perspective view which shows the state (state in which it inserted) the insulator 14 assembled | attached to the heating wire of FIG. The perspective view which shows the state (state in which it inserted) the insulator 15 assembled | attached to the heating wire of FIG. (A) is a perspective view of the heater terminal shown in FIG. FIG. 10B is a perspective view showing a state where the heater terminal of FIG. 9A in which the insulators 16 and 17 are interposed and the heating wire of FIG. 9 are connected. The perspective view of the protective tube with which the outer side of the heater main body shown in FIG. 2 is mounted | worn. FIG. 12 is a plan sectional view showing a state in which the heater main body shown in FIG. 2 and the protective tube shown in FIG. 11 are assembled (only the protective tube is broken). (A) is a top view of the insulator 12. FIG. (B) is a longitudinal sectional view of (a). (C) is a bottom view of (a). (D) is AA sectional drawing of (a). (A) is a top view of the insulator 13. FIG. (B) is a longitudinal sectional view of (a). (C) is a bottom view of (a). (D) is BB sectional drawing of (a). (A) is a top view of the insulator 14. FIG. (B) is a longitudinal sectional view of (a). (C) is CC sectional drawing of (a). (A) is a top view of the insulator 15. FIG. (B) is a longitudinal sectional view of (a). (A) is a top view of the insulator 16. FIG. (B) is a longitudinal sectional view of (a). (A) is a top view of the insulator 17. FIG. (B) is a longitudinal sectional view of (a). Explanatory drawing which shows the state by which the folding | turning front-end | tip part of the heating wire was linearly expanded by heat_generation | fever. The longitudinal cross-sectional view of the insulator 12 'which concerns on the modification of this invention. Explanatory drawing which shows the state where the folding | turning front-end | tip part was disconnected due to the linear expansion by the heat_generation | fever of a heating wire in the case of using the conventional insulator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 (a) and 1 (b), an in-furnace heater insulator (hereinafter simply referred to as an insulator) 12 according to the present invention and an in-furnace heater 1 (heat source) using the insulator 12 are applied. The furnaces F1 and F2 are illustrated as industrial heat treatment equipment. From the viewpoint of the heat distribution in the furnace and the heat treatment effect, a plurality of in-furnace heaters 1 may be installed in the vertical direction as in the heating furnace F1, or in a plurality in the horizontal direction as in the heating furnace F2. is there. The insulator 12 and the in-furnace heater 1 according to the present invention are not limited to a heating furnace having one door into the furnace, but a heating furnace provided with doors for entrance and exit (for example, It can be widely applied to continuous furnaces).

  As shown in FIGS. 2 and 3, an assembly 10 of a heater body (heating wire with an insulator) that constitutes a main part of the in-furnace heater 1 (see FIG. 12) includes a heating wire (heater wire) 11, an insulator 12. To 17 and the heater terminal 21.

  The heating wire 11 is formed by linearly extending a linear metal electrothermal material (for example, nichrome electrothermal material) from the proximal end toward the distal end, folding back into a U shape at the distal end side, and again at the proximal end side. A set of folding forms that return to a straight line is a set, and has a folded tip portion 11a and a double wire portion 11b. A plurality of sets of heating wires 11 having such a form are used to constitute one heating element as a whole.

  In this embodiment, for example, six sets of heating wires 11 are used, and four sets of the heating wires 11A are set to have substantially the same total length (effective heat generating portion) from the base end to the tip end. In the remaining two sets of heating wires 11B, one of the two base end portions is set longer than the other by a predetermined length, and this long set portion is welded to the heater terminal 21 (see FIG. 10). It functions as a lead portion 11c (welding margin) connected by the above.

  As shown in FIGS. 2 and 4, the insulators 12 to 15 are mounted in this order from the distal end side of the heating wire 11 toward the proximal end side (heater terminal 21 side). The insulators 16 and 17 are attached in this order from the proximal end side (heating wire 11 side) of the heater terminal 21 toward the distal end side. First, the insulators 13 to 17 will be described.

  As shown in FIG. 4 (b) and FIGS. 14 (a) and 14 (d), the insulator 13 is a reference for a set of line insertion holes through which one double line portion 11b in the heating wire 11 of each set passes. A disk-shaped base plate portion 13 a having a predetermined angular interval around the line L is provided. In this embodiment, twelve line insertion holes 13a1 are formed along a predetermined pitch circle P at equal angular intervals of an angle θ (= 30 degrees) corresponding to six sets of heating wires 11.

  The base plate portion 13a is provided with a connecting base portion 13b that protrudes toward the folded tip portion 11a of each heating wire 11 (see FIG. 14B). The connecting base portion 13b has a substantially columnar shape with the reference line L as the central axis (a shape in which the distal end side is tapered by a slight amount compared to the proximal end side), and is radially inward of each line insertion hole 13a1 of the base plate portion 13a. It is formed integrally with the part.

  The connection base portion 13b is formed with a circular and stepped insertion hole 13b1 having the reference line L as the central axis. The insertion hole 13b1 is appropriately used by incorporating a core rod for reinforcement and a sensor for temperature detection. The base plate portion 13a is formed with a regular quadrangular pyramid-shaped recess 13a2 communicating with the insertion hole 13b1 (see FIGS. 14B and 14C). At the tip of the connecting base portion 13b, there is formed a regular quadrangular pyramid-shaped convex portion 13b2 in which the bottom and height dimensions of the concave portion 13a2 of the base plate portion 13a are slightly reduced (FIGS. 14A and 14B). )reference).

  As shown in FIG. 5, a plurality of the insulators 13 configured as described above are used, and the protrusions 13 b 2 of any insulator 13 are fitted into the recesses 13 a 2 of the other insulators 13, so that the plurality of insulators 13 are used as a reference. In the direction of the line L, they are connected in a daisy chain. In this case, since the convex portion 13b2 and the concave portion 13a2 are formed in a regular quadrangular pyramid shape, relative rotation around the reference line L between the insulators 13 is prevented in a state where the insulators 13 are connected. Yes.

  As shown in FIG. 6, one double wire portion 11b of each heating wire 11 passes through the wire insertion hole 13a1 of each insulator 13, and the base end portion of each double wire portion 11b is shown in FIG. ), The base plate portion 13a of the insulator 13 disposed at a position closest to the base end side is projected. In this state, the lead portion 11c of one heating wire 11B and the lead portion 11c of the other heating wire 11B are connected to the double wire portion 11b of all the heating wires 11 as shown by arrows in FIG. The predetermined heating wires 11A, the predetermined heating wires 11A, and the heating wires 11B are connected by a columnar connecting member 19a or by a plate-like connecting member 19b so as to be connected in series.

  As shown in FIGS. 4 (c), 8 and 15, the insulator 14 has substantially the same shape as that obtained by removing the connecting base 13b from the insulator 13 and replacing the recess 13a2 with a circular through hole 14a. The base board portion 13a has line insertion holes 14b corresponding to the line insertion holes 13a1. The insulator 14 is inserted through only the lead portion 11c of each heating wire 11B (see FIG. 8), and is in contact with the end surfaces of the connecting members 19a and 19b on the plate surface where the wire insertion hole 14b is not formed. The arrangement position on the side is defined.

  As shown in FIGS. 4 (d), 9 and 16, the insulator 15 has a disk shape substantially the same size as the insulator 14, and a line insertion hole 15a through which only the lead portion 11c of each heating wire 11B is inserted. And is disposed in contact with the plate surface of the insulator 14.

  As shown in FIG. 4E, FIG. 10 and FIG. 17, the insulator 16 has a disk shape substantially the same size as the insulator 15 and has line insertion holes 16a through which only the heater terminals 21 are inserted. (See FIG. 10), the heating wires 11B are arranged in contact with the base end surfaces of the lead portions 11c.

  As shown in FIGS. 4 (f), 10 and 18, the insulator 17 has a two-stage cylindrical shape having a small diameter portion 17a and a large diameter portion 17b which are larger in diameter and thickness than the insulators 14-16. The wire insertion holes 17c for inserting only the heater terminals 21 are provided.

  As shown in FIG. 10A, the heater terminal 21 is a straight bar-like non-heating element, and includes a terminal plate portion 21a for connecting to a terminal on the power source (for example, AC power source) side at one end thereof. Yes. As shown in FIG. 10B, the heater terminal 21 includes an insulator 17, a heat insulating member 18 (for example, a plurality of round blankets), an insulator from the terminal plate portion 21a side toward the lead portion 11c side of the heating wire 11B. 16 are inserted in this order, and connected to the lead portion 11c of the heating wire 11B by welding in a state where the base end portion is in contact with the plate surface of the insulator 15.

  On the outside of the heater body assembly 10 (see FIG. 2) to which the insulators 12 to 17, the heat insulating member 18 and the heater terminal 21 are mounted, a cylindrical metal as a protective cover as shown in FIG. For example, a protection tube (radiant tube) 31 made of stainless steel is attached. The protective tube 31 includes a bottom portion 31a at the distal end portion and a flange portion 31b for fixing to the flange portions (see FIG. 1) of the heating furnaces F1 and F2 at the proximal end portion.

  In this embodiment, for example, as shown in FIG. 12, the heater body assembly 10 is placed in the protective tube 31 in a state where the lever 16 is diverted and seated on the bottom 31a of the protective tube 31 as a lever on the protective tube 31 side. The position of the distal end of the assembly 10 in the protective tube 31 is defined by bringing the lever 12 disposed on the distal end side into contact with the lever 16.

  In the state where the heater body assembly 10 is incorporated in the protective tube 31, a predetermined length of gap is formed between the outer surface of the insulators 12 to 16 and the inner peripheral surface of the protective tube 31, and the small diameter of the insulator 17 A very small gap is formed between the outer surface of the portion 17 a and the inner peripheral surface of the protective tube 31, and the large-diameter portion 17 b is seated on the flange portion 31 b of the protective tube 31.

  In the in-furnace heater 1 configured as described above, the heating wire 11 generates heat by energizing the heater terminal 21 from a power source (not shown), and the generated heat is radiated to the outside through the protective tube 31. The Rukoto.

  By the way, in this Example, the insulator 12 arrange | positioned at the front end side of the heating wire 11 has the shape which is common to the insulator 13, and the shape which is not common, as shown to Fig.4 (a), FIG.12 and FIG.13. It is comprised so that both shapes may be comprised. Specifically, as shown in FIG. 13, a set S of line insertion holes (one set of two line insertion holes 12a1) through which the double line portions 11b of the heating wires 11 of each set pass one by one is used as a reference. This is common in that it includes a disk-shaped base plate portion 12 a having a predetermined angular interval around the line L, and a connecting base portion 12 b that protrudes toward the folded tip portion 11 a of each heating wire 11.

  Similarly to the connecting base portion 13b of the insulator 13, the connecting base portion 12b has a substantially cylindrical shape with the reference line L as the central axis, and is integrally formed at a radially inner portion than the respective line insertion holes 12a1 of the base plate portion 12a. Yes. The connection base portion 12b is formed with a circular and stepped insertion hole 12b1 with the reference line L as the central axis, and the base plate portion 12a has a regular quadrangular pyramid-shaped recess 12a2 communicating with the insertion hole 12b1. Is formed. The concave portion 12a2 is formed to be approximately the same size as the concave portion 13a2 formed in the lever 13, and is fitted to the convex portion 13b2 of the lever 13 arranged on the base end side to be connected.

  On the other hand, such a partition wall is formed in that the first partition wall 12c and the second partition wall 12d are integrally formed on the folded tip end portion 11a side of each heating wire 11 of the base plate portion 12a. It is different from lion 13 without. Further, the connecting base portion 12b of the insulator 12 is different from the insulator 13 in which the protruding portion 13b2 is formed on the connecting base portion 13b in that a protruding portion for connection is omitted.

  The first partition wall 12c is connected to the base plate portion 12a at the lower end of FIG. 13B and to the connecting base portion 12b at the inner end, and projects radially (radially outward) around the reference line L. A set S of line insertion holes of the base plate portion 12a is partitioned for each set so that the adjacent folded tip portions 11a of the heating wires 11 are not short-circuited.

  The second partition wall 12d connects the projecting ends of the first partition walls 12c in a cylindrical shape, and any of the folded front end portions 11a of the heating wire 11 exceeds the direction away from the reference line L on the outer periphery of the base plate portion 12a. It partitions so that there is no. That is, the second partition wall 12d is formed so that all of the folded tip portions 11a of the heating wire 11 do not short-circuit with the inner peripheral surface of the protective tube 31 and all of the line insertion holes 12a1 of the base plate portion 12a and the protective tube 31. Partitions from the surrounding surface.

  The first partition wall 12c and the second partition wall 12d are set to have the same height from the plate surface of the base plate portion 12a. This height dimension is a length that does not exceed even when the folded tip portion 11a linearly expands in the direction of the reference line L when the heating wire 11 generates heat, that is, the wire diameter of the heating wire 11 is, for example, 5 to 5. When the length of the effective heat generating portion of the heating wire 11 is 1000 to 1500 mm and the diameter of the base plate portion 12a is 70 to 80 mm, for example, it is set to be about 15 to 30 mm. .

  When the insulator 12 configured as described above is arranged on the distal end side of the heating wire 11, as shown by a broken line in FIG. 19, an arbitrary set of a plurality of sets of double wire portions 11b is formed into a first partition wall. It is located between the adjacent ones of 12c and is folded in the vicinity of the first partition wall 12c. That is, the line portion that protrudes from the line insertion hole 12a1 in the “going direction” in the base plate portion 12a of the insulator 12 to the front end side is folded back in the vicinity of the adjacent first partition wall 12c, and the “return direction” of the base plate portion 12a. Through the line insertion hole 12a1 and return to the base end side.

  These first partition walls 12c prevent a plurality of sets of double line portions 11b from coming into contact with each other at a portion extending from the line insertion hole 12a1 of the base plate portion 12a toward the tip side (short circuit). That is, even if the double wire portion 11b of each heating wire 11 is linearly expanded in a different manner due to heat generated by energization, or even if it is thermally deformed so that the loop of the folded tip portion 11a spreads, there is the first partition wall 12c. At that time, it is further prevented from approaching the adjacent folded tip 11a side, and finally the folded tip 11a extends in the direction of the reference line L as shown by a two-dot chain line in FIG. Thus, a short circuit between the folded tip portions 11a is prevented.

  Further, when the in-furnace heater 1 configured as described above is used, thermal deformation is performed so that the folded tip portion 11a of the double wire portion 11b of each heating wire 11 is warped in a direction away from the reference line L due to heat generated by energization. Even if it is going to be, since there is the 2nd partition wall 12d, it will be prevented from approaching to the inner peripheral surface side of the protection tube 31 further, and finally, as shown with a dashed-two dotted line in Drawing 19, The folded front end portion 11a extends in the direction of the reference line L, and contact (short circuit) with the inner peripheral surface of the protective tube 31 is prevented.

(Modification)
The insulator 12 does not need to be connected to other insulators 13 or the like on the distal end side, and may simply be in contact with the insulator 16 or the like on the protective tube 31 side. Therefore, in the above embodiment, the connecting base end portion 12b is used. However, it is also possible to form the insulator 12 by using a mold for forming the insulator 13. Therefore, in this case, as shown in FIG. 20, for example, a protrusion 12b2 having substantially the same shape as the insulator 13 is formed at the tip of the connecting base end portion 12b of the insulator 12 ′. You may comprise an in-furnace heater using 12 '. In FIG. 20, the configuration other than the convex portion 12 b 2 is the same as that of the insulator 12. Therefore, the same reference numerals are given to portions that perform the same functions as the insulator 12, and the description thereof is omitted.

  In the above-described embodiments, the insulator 12 or the insulator 12 ′ and the insulator 13 or the insulators 13 are fitted to each other by fitting the concave-convex portion 12a2 and the convex portion 13b2 or by fitting the concave portion 13a2 and the convex portion 13b2. Therefore, the relative rotation around the reference line L is prevented. However, the concave and convex portions are not limited to a quadrangular pyramid shape, and may be, for example, a half moon shape.

  Further, the base plate portion 12a of the insulator 12 or the insulator 12 'is not limited to the disc shape, and may be formed in, for example, a regular polygon shape. Correspondingly, the protective tube 31 may be formed in a regular polygonal cylinder, for example.

F1, F2 Heating furnace 1 In-furnace heater 10 Heater body (heating wire with insulator) assembly 11, 11A, 11B Heating wire 11a Folding tip 11b Double wire portion 11c Lead portion 12-17 Insulator 12a Base plate portion 12a1 wire Insertion hole 12a2 Recess 12b Connection base 12b1 Insertion hole 12c First partition wall 12d Second partition wall 21 Heater terminal 31 Protective tube

Claims (2)

There are a plurality of sets of double line portions that are formed from a heating wire folded back that extends from the base end toward the front end, is folded back at the front end side, and returns to the base end side again. In order to prevent short-circuiting between sets of double wire portions, a plurality of insulators for in-furnace heaters are arranged so as to pass each heating wire of the double wire portion independently from the base end to the tip of the heating wire Because
Among the plurality of in-furnace heater heaters, the insulator disposed at the tip portion is a set of line insertion holes that pass through the double line portions of each set one by one at a predetermined angular interval around the reference line. With a base plate part
A set of the line insertion holes is provided so that the base plate portion protrudes radially around the reference line at the folded tip portion side in each double line portion of the heating wire, and adjacent folded tip portions are not short-circuited. The first partition walls for partitioning each set and the projecting ends of the first partition walls are connected in a cylindrical shape, and any of the folded tip portions does not exceed the outer periphery of the base plate portion in a direction away from the reference line. An insulator for an in-furnace heater, wherein the second partition wall partitioning in this way is integrally formed. There are a plurality of sets of double line portions that are formed from a heating wire folded back that extends from the base end toward the front end, is folded back at the front end side, and returns to the base end side again. In order to prevent short-circuiting between sets of double wire portions, a plurality of insulators for in-furnace heaters are arranged so as to pass each heating wire of the double wire portion independently from the base end to the tip of the heating wire With
Adjacent ones of the in-furnace heater heaters can be connected to each other, and outside the assembly of the heating wire with the insulator to which the plurality of in-furnace heater heaters are connected, A furnace heater equipped with a metal protective cover,
Among the plurality of in-furnace heater heaters, the insulator disposed at the tip portion is a set of line insertion holes that pass through the double line portions of each set one by one at a predetermined angular interval around the reference line. With a base plate part
A set of the line insertion holes is provided so that the base plate portion protrudes radially around the reference line at the folded tip portion side in each double line portion of the heating wire, and adjacent folded tip portions are not short-circuited. A first partition wall for partitioning each set, and projecting ends of the first partition walls are connected in a cylindrical shape, and the line insertion holes are arranged so that none of the folded tip ends are short-circuited with the inner peripheral surface of the protective cover. An in-furnace heater, wherein the second partition wall that partitions all of the protective cover and the inner peripheral surface of the protective cover is formed integrally.

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